Abstract

Charge-neutral excitons in semiconductor quantum dots (QDs) have a small finite energy separation caused by the anisotropic exchange splitting. Coherent excitation of neutral excitons will generally excite both exciton components, unless the excitation is parallel to one of the dipole axes. We present a polaron master equation model to describe two-exciton pumping using a coherent continuous wave pump field in the presence of a realistic anisotropic exchange splitting. We predict a five-peak incoherent spectrum, namely a Mollow quintuplet under general excitation conditions. We experimentally confirm such spectral quintuplets for In(Ga)As QDs and obtain very good agreement with theory.

Figures (3)

Schematic of the QD under continuous wave pumping with a field that is polarized along, e.g., θ=(π/4) in a weakly coupled planar cavity. This QD can be excited with electric dipole along the x or y axis; the double arrows show the polarization of the laser.

Incoherent spectrum S(ω) with (blue, solid) and without (red, dashed) phonon scattering. The Rabi frequencies are Ω1′=Ω′cosθ and Ω2′=Ω′sinθ, and γ1,2=γ1,2′=1μeV, δ12=−12μeV, and α1,2=1. (a) Ω′=30μeV, with different θ. (b) θ=π/8, with different Ω′.